How does the EZ efi determine what AFR the engine will run at? We use the heck out of the new Holley HP system, it is self learning and tuning, but we still have to determine the AFR we want it to run at

you plug in desired a/f at idle, cruise, and wot.

So you're telling a guy that has experience with EFI of different types and 2 cars that run very well with a particular setup that they don't work properly?

Yes, the referenced fuel pressure regulator is a must for any EFI system... especially EZ EFI.

Most people... even experienced tuners miss this one because they don't understand how it works.

I understand the reason for it, but I will disagree that it's a must on all systems. I've done many with and without the reference line, and they all ran perfect.

I also understand and I also must disagree. When you say "must", it means the system can not function without it. That is clearly not the case. Maybe separating preference from requirements is the issue here. :cheers:

No, for it to work properly... and if you actually did some testing with the injectors and saw what they did when you didn't reference them... you would know why.. For the EZ EFI it is a must since the ECU uses fuel pressure as a reference.

Really all efi systems should be this way. People get lazy or think there is no reason for it but there is.

So, if you understand how it works then your saying it is correct for the injector to flow more fuel at an idle than it does at WOT?

of course not. But referencing the regulator will lower the fuel pressure at idle/cruise/higher vacuum areas, and increase it as the load increases and vacuum drops. In an adjustable system (not the EZ EFI) you can set the injector pulse width to compensate for a non-changing fuel pressure. Now an injector has a minimum amount of time it takes just to function, so if you have a real large (or too large) injector you can have idle issues and the lower fuel pressure with referencing would help. But I've run 95# injectors without issue. I boost reference for blown engines, but again have done many N/A setups without referencing and never noticed a single hiccup.

I am not challenging your knowledge, I'm just a home hobby tuner guy. I just can't see the issue you're describing.

ok, so you really don't understand. I am not having a pissing contest either... Greg is a really nice guy and from the same area I'm from too. I am just trying to debunk some bad info that I read.

So, really the reason you touched on is the injector flow... yes they have a minimum time it takes to open "dead time" but what we want it to keep the pressure differential across the injector constant so we just tune the fuel curve and not chasing an injector that flows different amounts of fuel at different engine vac.

when you do not reference the regulator here is what you have. At idle and cruise when you have hi vac the injector will actually flow more fuel without the line connected because the pressure is say 45psi and under vac to it helps pull fuel out of the injector, so....net you have more fuel flow if you have no vac reference. So 45psi and -10psi equals a net of 55psi flow... the injector will flow more fuel in this vac area without the line connected. The problem is worse as the injector size gets larger.

Now if you do reference the regulator you have 45psi fuel pressure... and say -10psi vac you have 35psi fuel pressure and -10psi still equals 45psi net... the injector flow rate stays the same. As the injector sees less vac then it keeps the same net flow rate across the injector no matter what the engine vac or boost does. That is why you actually boost reference the regulator... so the boost does not push the fuel back into the rail. 45psi... 10psi boost 45psi + 10psi = 55psi but still a net of 45psi fuel pressure since the intake has 10psi in it.

You will find that if you use the vac referenced regulator and actually use it all the time it will make tuning easier.

Now "opening time" or "dead time" is something totally different... it is the minimum actual time it takes for the injector to open and start flowing fuel.. That is a different table and not a table for tuning... it should be a compensation for each style of injector. If that table isn't correct then when you ask for a 5% change in fuel you may only be getting a 3% change actually. Having a referenced fuel pressure regulator effects the opening time some since the vac makes it easier to open the injector but that is part of the reason the reference helps there too. Most aftermarket ECUs only use injector dead time as a reference in voltage vs time and don't take in account fuel pressure as a third axis. GM does in the KPA vs flow rate in the LS computers. And a second table as injector flow vs battery voltage.

Injector dead time/opening time is a value added back to the commanded injector pulse width that is programmed into the ecu... it is even more important as RPM gets real hi and the actual time to get the job done gets shorter.

Now that we said all of that... the EZ EFI especially needs this because when you enter the fuel pressure... it assums that the given pressure is at rest with no vac line... that decided how much pressure you have off what the map sensor shows. Then it decides how much PW it needs to maintain a target A/F ratio. It will have a harder time tuning itself when it is assuming the fuel pressure is lower than it really is.

Boosted I reference it, N/A I sometimes do and sometimes don't. I like to run rear-mounted regulators too so that's a whole 'nother area we might argue about........... :D

I appreciate the info.